Blue Moon said Platina had not been able to fulfill the initial earn-in requirement to drill 10,000m within the prescribed timeframe.
Platina said it had withdrawn following the prolonged suspension of field activities in the US due to the COVID-19 pandemic.
Managing director Corey Nolan said Platina's revised strategy was to redirect its focus to assets in Australia as international restrictions persisted.
Blue Moon CEO Patrick McGrath said Platina's initial drilling had increased Blue Moon's confidence in the project and renewed its commitment to drill and develop the asset in 2021.
Platina had reported highlights including 1.71m at 51.9% zinc, 1.49% copper, 0.05% lead, 0.85g/t gold and 31.9g/t silver, after drilling two diamond holes at Blue Moon late in 2019.
Blue Moon was set to plan an aggressive follow-up drilling programme.
"The value of the project has also been enhanced by the recent increase in price for zinc, copper, gold and silver," McGrath said.
The project has an inferred resource of 7.8 million short tons at 8.07% zinc equivalent for about 771 million pounds of zinc, 71Mlb of copper, 300,000 ounces of gold and 10 million ounces of silver.
Nolan said Platina would retain six million shares in Blue Moon Zinc after acquiring a 5% equity interest in the company as per the deal struck in August 2019.
Blue Moon shares (TSXV: MOON) touched a one-year high intraday of C7.5c but closed 1c or 13.5% lower at 6.5c, to value it at $7.8 million (US$6 million).
Platina shares (ASX: PGM) have ranged from A1c-8.2c this year and closed up 4.6% to 4.5c today, capitalising it at $18 million (US$13 million).